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Christine Tobler


MathWorks

180 total contributions since 2015

Professional Interests: numerical linear algebra, graph algorithms

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Answered
could anyone help me to calculate the euclidean distance for the matrix.
For MATLAB R2017b or later, you can use the vecnorm function for a simpler construction than the one involving sqrt, sum, and .^...

7 days ago | 1

Answered
Hi just want to know if someone can maybe help me i have this matrix t want to get the eigenvector but it give me complex values and im pretty sure it must not be complex values for that matrix
A simple way to verify if the returned eigenvalues are correct is to compute both the eigenvalues and the eigenvectors, and to c...

25 days ago | 1

Answered
How can I solve a sparse linear system efficiently in MATLAB?
Do you need the whole matrix A*inv(B)*A', or do you just need to apply this matrix to a vector (A*inv(B)*A'*x)? In the second ca...

1 month ago | 0

Answered
Backslash (\) operator became much slower when updating from 2015b to 2019a
Thank you for these logs. The difference in behavior comes from the following message, saying that we repeat the factorization w...

2 months ago | 1

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Answered
Backslash (\) operator became much slower when updating from 2015b to 2019a
Based on the spy plot, I would be astonished if a different method was selected between the two releases - I think the LU solver...

2 months ago | 1

Answered
Backslash error ''Warning: Matrix is singular to working precision."
For more details about what backslash does for sparse matrices, use spparms('spumoni', 1) cnew = Amat \ rhs; This will displa...

3 months ago | 1

Answered
SVD freezes in 2018a
This sounds like a bug. It shouldn't be due to memory issues, SVD uses the same amount of memory if the matrix size and the synt...

3 months ago | 0

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Answered
generalized eigen-problom, complex non-symmetric matrix, how to find orthogonal eigenvectors
There's an easier way to compute both U and W: [U, D, W] = eig(A, B); This will make sure that the eigenvectors U(:, i) and V(...

3 months ago | 1

Answered
Optimizing a matrix with cplexlp?
You can solve this using intlinprog. This is probably not the most efficient way of solving the problem, but reliable A = [0 1 ...

3 months ago | 1

Answered
How SVD works for dimensionality reduction?
There's the svd function. The link points to the doc which has examples of how to use it.

4 months ago | 0

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Answered
chol fails on Hermitian positive definite matrix?
That is astonishing. The matrix is not badly conditioned, I would expect CHOL to work fine here. I tried on my machine and didn...

4 months ago | 0

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Answered
Sparsest solution for A\B
That statement is wrong, x = A\b doesn't return the solution x with the smallest number of nonzero elements. What mldivide does,...

4 months ago | 2

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Answered
eigs function: incorrect eigenvalues
The problem is that the matrix A is badly conditioned: >> cond(full(A)) ans = 2.206837183464466e+16 This is just around...

4 months ago | 2

Answered
Plotting eigenmodes in 3D
Depending on the format of your 3D-frame, maybe you could use pdeplot3d.

4 months ago | 0

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matchpairs function in r2019a
The algorithm solves the same problem as the Hungarian algorithm, but it's not the same algorithm. The Hungarian algorithm has c...

5 months ago | 0

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Answered
Hungarian algorithm realizated in matlab
As of R2019a, there is a function matchpairs in core MATLAB (no toolboxes needed) that solves the same problem as the Hungarian ...

5 months ago | 0

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Hungary algorithm
As of R2019a, there is a function matchpairs in core MATLAB (no toolboxes needed) that solves the same problem as the Hungarian ...

5 months ago | 1

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Matching of eigenvalues of 2 matrices
With R2018a, there is a new function matchpairs which might be useful for this. Basically, it takes a matrix of similarities bet...

5 months ago | 0

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Answered
How to calculate n-th eigenvector using eigs() function
There's no way of doing this directly, and the indirect ways are hard to implement and not very robust. Also, this will be very...

5 months ago | 2

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Answered
Simulating a Markov chain
There is a specific class that represents a discrete-time Markov chain in the Econometrics toolbox: dtmc.

5 months ago | 0

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Delete Highlighted Node in a Graph?
You can use highlight to set that marker to 'none'. The GraphPlot object h contains all the graphical properties of the plotted ...

5 months ago | 0

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Answered
Yet another lu(A) question and pivoting
I'm afraid I can't post the algorithm used in mldivide. Note that it's a bit more general: it also works if both the rows and th...

5 months ago | 0

Answered
Yet another lu(A) question and pivoting
Yes, MATLAB checks if L is a permuted triangular matrix. See the doc for mldivide - Algorithm for full inputs. However, it's st...

6 months ago | 1

Answered
In sparse matrix eigs(A,k,sigma), how to specify both shift and direction
With a numeric sigma, EIGS uses a linear system solve (A-sigma*I)\v instead of A*v to compute the largest eigenvalues of the inv...

6 months ago | 0

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Answered
Is there a way to obtain all cycles of a directed graph similar to all_simple_cycles() in sage?
There's no direct function, but I've attached a solution I've quickly put together just now. This recursively iterates through a...

6 months ago | 0

Answered
How to generate all the matrices of graphs for given numbers of vertices and edges?
I've attached a script that computes this for n=4 and e=3. This script will not scale well to larger numbers of nodes and edges,...

6 months ago | 0

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Which algorithm eig () function use ?
There are different algorithms for solving eigenvalue problems, depending on the properties of the inputs. The most well-known s...

6 months ago | 0

Answered
Shotest path between any two nodes in the graph
To read data from Arcmap, you would probably need to use the Mapping Toolbox (for example shaperead). To use the shortest path a...

7 months ago | 0

Answered
graph weight overlap and arrow size
There isn't a solution for this at the moment, unfortunately. One alternative would be to set the LineWidth based on the edge we...

7 months ago | 0

Answered
Is it possible to set an alpha value for each edge in a GraphPlot?
Hi Michael, We do not provide a way to set EdgeAlpha to be different for each edge. We just didn't expect this to be very usefu...

7 months ago | 0

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